1. Field of the Invention
The present invention is included in a technical field of processes of semiconductor device fabrication and the like, and more specifically, relates to, for example, a substrate processing method for performing gelling processing when a coating film in a sol form in which particles or colloids are dispersed in an organic solvent applied on a substrate as an insulating film material.
2. Description of the Related Art
In processes of semiconductor device fabrication, a layer insulating film is formed, for example, by an SOD (Spin on Dielectric) system. In this SOD system, a layer insulating film is formed by coating a wafer with a coating film while spinning the wafer and performing chemical processing, heat processing, or the like for the wafer by means of a sol-gel process or the like.
When a layer insulating film is formed by the sol-gel process, for example, first an insulating film material, for example, a solution in which colloids of TEOS (tetraethoxysilane) are dispersed in an organic solvent is supplied onto a semiconductor wafer (hereinafter referred to as "wafer"). Then, the wafer to which the solution has been supplied is subjected to gelling processing, and then solvents are exchanged. Subsequently, the wafer on which the exchange of solvents has been performed is subjected to heat processing.
In the process in which the wafer is subjected to gelling processing (aging processing) out of these series of processes, the wafer is subjected to heat processing at a temperature of, for example, about 100.degree. C. on a hot plate in a processing chamber which is configured such that a processing gas made by mixture of, for example, ammonia gas and water vapor is exhausted while being supplied. Since water vapor is contained in the processing gas as described above, colloids of TEOS contained in a coating film applied as an insulating film material are gelled to be chained in a network form. The coating film immediately after the gelling contains water. After the water in the coating film is exchanged for another solvent, the solvent is removed to dry the coating film, thereby obtaining an insulating film. Alternatively, the water in the coating film is removed to dry the coating film, thereby obtaining an insulating film. There is a disadvantage that such removal of the water in the coating film requires very long total processing time.
Hence, to solve the above disadvantage, it is conceivable to reduce a ratio of water vapor contained in the processing gas by way of example. However, in that case, a reaction speed for collides of TEOS to be gelled and chained in a network form reduces, thereby bringing about a disadvantage that time required for the aging processing becomes lengthy. Further, water functions as a heat transmission medium for transmitting heat from the hot plate to the wafer during the heating. Therefore, if water is limited, there arises ununiformity in heat which is transmitted from the hot plate to the coating film applied on the wafer, resulting in occurrence of projections and depressions on the surface of the formed layer insulating film. Consequently, the projections and depressions cause insulation failure or the like in wiring which is formed thereon.